Cellular mobile radiotelephone (CMR) service has been in widespread use for several years. Typical systems are characterized by dividing a radio coverage area into smaller coverage areas or "cells" using low power transmitters and coverage-restricted receivers. CMR systems are described in U.S. Pat. Nos. 3,906,166 and 4,268,722. As will be known to those skilled in the art, the limited coverage area enables the radio channels used in one cell to be reused in another cell. As a cellular mobile radiotelephone within one cell moves across the boundary of the cell and into an adjacent cell, control circuitry associated with the cells detects that the signal strength of the telephone in the just-entered cell is stronger, and communications with the radiotelephone are "handed off" to the just-entered cell.
A cellular mobile radiotelephone system typically utilizes a pair of radio frequencies for each radio channel in each cell. Each cell typically includes at least one signalling channel (also called a control or access channel) and several voice channels. The signalling channel is selected or dedicated to receive requests for service from mobiles and portables, to page selected mobiles or portables, and to instruct the mobiles or portables to tune to a predetermined voice channel where a conversation may take place. The signalling channel is responsible for receiving and transmitting data to control the actions of the mobiles and portables.
The data message and radio channel specifications for U.S. cellular radiotelephone systems are set forth in Electronic Industries Association/Telecommunications Industry Association (EIA/TIA) Standard 533 (previously known as Interim Standard CIS-3) implemented in accordance with 47 C.F.R. 22, in the Report and Orders pertaining to Federal Communications Commission (FCC) Docket No. 79-318. Copies of the EIA/TIA-533 may be obtained from the Engineering Department of the Electronic Industries Association at 2001 Pennsylvania Avenue, N.W., Washington, D.C. USA 20006.
Increasingly, users of cellular mobile radiotelephones travel between cities having cellular systems operated by different operating companies. In addition, the FCC has established that each area wishing to establish a cellular telephone network may have up to two cellular system operators, and therefore parallel but separate systems are in place in most major metropolitan areas. While the mobile radiotelephones for use in these different systems are identical, the cellular systems are configured so that only cellular telephones which are identified as "home" units or subscribers within a given cellular system may communicate within a given operator's system.
It is known that when a cellular mobile radiotelephone originates a call, it transmits a series of data messages to the serving cell. These messages, referred to as a Call Origination, are defined by EIA/TIA-533. These data messages always contain the low order seven digits of the unit's telephone number, known as the Mobile Identification Number (MIN), the unit's Station Class Mark (SCM), which identifies functional characteristics of the unit, and the Called Address, or dialed telephone number. Although optional, cellular system operators typically also require additional data words to be transmitted that contain the MIN2, which is the high order three digits or NPA of the cellular unit's telephone number, and the Electronic Serial Number (ESN).
These data messages are provided first to the cell, and then through a data link to the mobile telephone switching office ("MTSO"). The MTSO, also known as "the switch", makes voice connections between mobile radiotelephones and the main telephone network. At the MTSO, a determination is typically made whether the radiotelephone is an authorized user or subscriber by looking up the telephone number, serial number, and other information provided by the radiotelephone to see if there is an entry in the MTSO's database corresponding to that particular telephone. Part of the normal, but optional, functions of an MTSO is to validate that the ESN and MIN received as part of a Call Originalion message are valid. If the MIN is valid and "home", the received ESN is compared to the MTSO's database ESN entry to detect fraud. If these checks succeed, the call is allowed to proceed.
It is also known that a cellular mobile radiotelephone, when it first powers up or first enters the cell of a CMR system when already powered up, can optionally be instructed to identify itself as actively present within a particular cell and on the system. The radiotelephone identifies itself or "registers" through a process known as Autonomous Registration by providing a data packet similar to that of a Call Origination. The original design intent of Autonomous Registration was to improve the efficiency of potential future call deliveries by keeping the MTSO informed of the approximate whereabouts of each individual cellular unit, and to reduce paging channel load by lessening the need to page all cells to find a cellular unit. When the MTSO is thus informed, it can "page" (i.e., attempt to ring) the cellular unit only in the cell or area that it was last known to be in. Additional cells would be paged only if the mobile was not found with the initial page.
While most cellular systems support the Autonomous Registration feature, processing of the received identification information is usually proprietary to the vendor of the MTSO equipment. However, it will be observed that the data contained in an Autonomous Registration message is essentially the same as a Call Origination. The difference is that an Autonomous Registration is not associated with a call attempt, and is not necessarily used to validate a cellular unit's ability to place or receive calls. Instead, an Autonomous Registration is simply a set of messages periodically and autonomously sent from the mobile to the serving cell at an interval specified in data parameters previously received from the cell by the cellular unit.
For purposes of the present application, the terms "register", "registration", etc. will be used to denote the provision of identification information by Call Origination, Autonomous Registration, or other means.
It is further known that in CMR systems, a subscriber's ability to receive incoming calls outside his or her home service area is restricted. A subscriber using or attempting to use his or her cellular mobile radiotelephone in a service area outside his home service area is said to be "roaming", and he or she is commonly referred to as a "roamer". When cellular telephone subscribers leave the area of their subscribed service, they frequently do not use their cellular telephones because they do not know (or have forgotten) the particular procedures for operating their radiotelephone as a "roamer" in the newly-entered service area. Lack of use of the radiotelephone in different service areas results in a loss the benefits of cellular telephone service to the subscriber, and a loss of revenue both from the calls that would otherwise be made by the roamer and from calls to the roamer which cannot be completed because the roamer's home service area does not know where to forward the calls.
Even though a subscriber is not always aware of having travelled beyond the range of the home service area, CMR systems are designed to detect this situation and so apprise the user, in the following manner. Each cellular system has been uniquely assigned a System IDentification (SID) number. Electrical signals corresponding to each cellular system's SID are continuously transmitted by that system over a control channel. The SD of the system from which a particular subscriber has agreed to acquire CMR services is programmed into a Numerical Assignment Module (NAM) or memory incorporated into the subscriber's mobile radiotelephone unit.
When a subscriber's mobile radiotelephone unit is "powered up" or first enters the area of coverage of a CMR system when already powered up, it selects the strongest detectable control channel and receives a system parameter overhead message in the form of an overhead message train (OMT). The OMT includes the 15-bit SID of the CMR system whose signal the mobile unit is receiving. The mobile unit then compares the transmitted SID to the SID programmed into its NAM to determine identicality. If the unit determines lack of identicality, it is indicated that the unit is "roaming". In many cellular radiotelephone units, a "roam" indicator light is activated on the control panel associated with the unit. In this manner, a subscriber is made aware that his or her mobile radiotelephone unit has seized or entered a system other than the system on which he or she is an authorized subscriber.
A roamer who desires to place an outgoing call typically must then access the CMR system in which he or she is roaming through procedures established by the CMR system operator. These procedures typically involve special codes, key sequences, and information solicitation from the subscriber so that the roamer is aware that he or she will be billed at the rates established for roaming services (instead of the usual "home" service rate).
Further difficulties are encountered when a roamer desires to receive incoming calls when in a foreign service area. In order for a roamer to receive incoming calls, it is typically required that would-be third-party callers know the whereabouts of the subscriber. Unanswered calls placed to the subscriber's home number are typically answered with a message indicating that the subscriber cannot be found. If the caller knows the CMR system in which the roamer is present, then there are procedures provided for accessing the subscriber through the facilities of that CMR system. This requires the caller to know the roamer's itinerary and the roamer access number of the CMR system in which the roamer is present. Many major service areas have a 10-digit roamer access number. Armed with this and other information, a would-be caller may dial the 10-digit roamer access number of the CMR system in which the roamer is present. Then, the caller dials the roamer's home number, including home area code, and the call will be delivered.
This unwieldy procedure can sometimes be exacerbated by the need for the subscriber to arrange the right to have incoming calls delivered with the CMR service provider in the foreign area.
Needless to say, procedures for arranging for roaming service such as these require advance planning, scheduling, and dissemination of itinerary information to persons who may want to call the subscriber in a foreign service area. These cumbersome procedures inhibit the flexibility and freedom prized by many cellular telephone subscribers, and also reduce the likelihood that a subscriber will avail himself or herself of roaming services in a foreign area. Moreover, the requirement for advance arrangement of roaming services simply precludes the use of roaming services by subscribers who, because of reasons beyond their control and foresight, find themselves in a foreign service area without any guidance as to the procedures for access to roaming services, and must place a call or other inquiry to the CMR system operator. Obviously, the subscribers in such circumstances are deprived of the convenience and benefit of their cellular mobile radiotelephones and the CMR system operators miss the opportunity to earn revenue.
Some CMR systems, for example, U.S. Pat. No. 4,901,340, of Parker et al., "System for the Extended Provision of Cellular Mobile Radiotelephone Service", also known as the GTE Mobilenet Incorporated "Follow-Me-Roaming" (trademark) service, are provided to ameliorate many of these difficulties and make the use of roaming services in foreign service areas more convenient. However, even with such services as the "Follow-Me-Roaming" service, it is required that the "Follow-Me-Roaming" service system hardware and software be implemented in the CMR system. Such systems, although they provide many advantages to roamers, do not accommodate the roamers who are from systems that do not have the "Follow-Me-Roaming" service or other types of following services. Again, the subscribers are deprived of the benefit of their cellular mobile radiotelephones and the CMR systems lose revenue from potential customers.
When considering the nature of the problem with accommodating roamers, the present inventor has discovered certain key aspects of the nature of the difficulty with roaming services. One key aspect in the provision of convenient roaming services involves the detection of the presence of roamers, who by definition are not subscribers in the CMR system, within a CMR system. Once the roamers are detected, another key aspect is the ability to contact these roamers for the purpose of providing information in a convenient manner concerning access to roaming services.
Considered in these terms, yet another key aspect involves the detection that a particular mobile radiotelephone is a member of a certain class of mobile radiotelephones, for example, roamers, or home unit owners of a certain type of mobile radiotelephone, or home subscribers having a certain prefix in his or her NPANXXXXXX. Once the presence of members of a certain class have been detected as present (and active) in the CMR system, it is possible to consider directing a class-targeted communication to members of that certain class, by placing calls to members of the class with an automated contacting means. As examples, for roamers, information concerning the provision of roaming services may be provided; for owners of certain types of telephones, information concerning newly available features may be provided; for subscribers having a certain prefix in his or her telephone number, an automated survey may be conducted or the acceptance of particular special telephone services provided by the CMR system operator (e.g. voice messaging or call waiting) may be interactively solicited.
Prior to the present invention, there has been no way to selectively determine whether a registering mobile radiotelephone is a roamer, or a home unit, or for that matter, to determine whether the registering mobile radiotelephone possesses other predetermined class characteristics, and to provide services to directed specifically to that class of telephones. Accordingly, there is a need for an automated system capable of detecting mobile radiotelephones by class, for example roamers, and for proactively contacting selected mobile radiotelephones for the purpose of the providing provision of information and interactive service solicitation.